This invention relates to the treatment of liquids by exposure to ultraviolet (UV) radiation. An aspect of the invention includes monitoring the effectiveness of UV treatment.
It is often desirable, even necessary, to treat aqueous liquids, particularly water, so as to ensure its potability.
The treatment of household water, be it obtained from a municipal water distribution system, in which it has previously been treated, or from a well is often desired. A number of approaches has been developed, including the use of filters, distillation, reverse-osmosis, ultraviolet (UV) light, etc.
There are xe2x80x9cpoint-of-usexe2x80x9d systems where a user treats the water immediately prior to use, as by pouring water through a filter, e.g., an activated carbon filter.
There are xe2x80x9cpoint-of-entryxe2x80x9d treatment systems where the water is generally treated without the active involvement of the user, except for possibly maintaining the system. In a point-of-entry system the water is generally treated prior to release from its pressurized distribution system. The treatment system may thus be located in a household, for example, such that all water passing from the external source of water to be distributed within the household is treated. Sometimes, such a system is located so as to ensure treatment of water that is expected to be consumed, but to leave untreated water to be used for other purposes, such as washing clothes or lawn watering. This cuts down on wear on the treatment system and can improve economies of use.
In any case, UV-treatment is often regarded as a desirable approach for treating water that is to be protected against the presence of microorganisms that might be found therein. It is in the area of pressurized (e.g., point-of-entry) systems that the invention disclosed herein finds use.
A prior art system related to the present invention is described in the specification of U.S. Pat. No. 5,247,178, issued to Ury et al. on Sep. 21, 1993, the specification of which is incorporated herein by reference.
A broad aspect of the present invention is an apparatus for treating a pressurized liquid in which the apparatus includes:
a pressurized liquid treatment chamber having an inlet end and an outlet end, the chamber having a window, preferably quartz, permeable to UV light;
a UV light source outside of the chamber located such that it emits light through the window into the chamber to expose liquid within the chamber to the emitted light and treats the liquid;
a shaft which extends between the inlet end and the outlet end of the chamber, located to turn about a central axis of the chamber extending between the inlet end and the outlet end;
a flexible cleaning member affixed to the shaft and extending radially therefrom to flexibly engage an interior surface of the window for cleaning thereof as the shaft turns; and
at least one member extending radially from the shaft into the treatment chamber to disrupt axial flow of water through the chamber.
In a preferred embodiment, the chamber window is a circular cylinder made of quartz, quartz being permeable to UV light.
The member extending from the shaft disrupts axial liquid flow, i.e., precludes linear flow parallel to the central axis of the cylinder as the liquid travels through the cylinder. This disruption serves to bring water near the center of the tube towards the window bringing it into better exposure to the UV light. This permits a relatively large proportion of the total volume of the cylinder to be occupied by water travelling through the treatment chamber. In the disclosed embodiment, total usable volume is about 90 percent. Alternatively, the amount of the treatment chamber defined by the cylinder that is free to be occupied by the pressurized liquid is at least 50 percent of the total volume of the cylinder; or is at least about 55 percent of the total volume of the cylinder; or is at least about 60 percent of the total volume of the cylinder; or is at least about 65 percent of the total volume of the cylinder; or is at least about 70 percent of the total volume of the cylinder; or is at least about 75 percent of the total volume of the cylinder; or is at least about 80 percent of the total volume of the cylinder; or is at least about 85 percent of the total volume of the cylinder; or is at least about 89 percent of the total volume of the cylinder.
The member that extends radially from the shaft has a surface transverse to the axis, the obverse face of which faces the inlet end of the chamber. In the embodiment detailed below, each such member or xe2x80x9cwingxe2x80x9d has an obverse face with cross-sectional area of about 8 percent of the inner cross-sectional area of the tubular cylinder. The cross-sectional area of a wing is generally at least about 5, 6, or 7 percent of the inner cross-sectional area of the tubular cylinder. In certain embodiments, the cross sectional area is equal to at least 9 or 10 percent of the area of the cross section of the cylinder, or about 15, or about 20, or about 25 percent of the area of the cross section of the cylinder.
In a preferred aspect, the apparatus of the invention includes, but is not limited to, three pairs of wings, in which the wings are spaced along the shaft. There is thus a first pair of wings (each wing of a pair angularly spaced from the other of the pair) axially located nearer to the inlet end of the cylinder than to the center (mid-plane) of the cylinder, a second pair of wings located nearer to the center of the cylinder than to either of the inlet or outlet ends of the cylinder, and a third pair of wings axially located nearer to the outlet end of the cylinder than to the center to of the cylinder.
Usually, there is at least one member that is located nearer the inlet end of the chamber than the outlet end. If there is a second member, the first and second members are spaced apart from each other. They can be angularly spaced from each other, or they can be axially spaced from each other, or they can be both axially and angularly spaced from each other.
Preferably, the combined cross sectional areas of the obverse faces of the members is at least 30, or at least 40, or at least 50, or at least 60, or at least 70, or at least 80, or at least 90, or at least 100, or at least 150, or at least 200, or at least 250, or at least 300 percent of the area of cross section of the cylinder. In the disclosed embodiment, the area of each wing is about 8 percent and there are six wings for total surface area of about 48 percent. It is thus preferred that the total obverse surface area presented by the wings be at least about 48 percent of the area of cross section of the cylinder.
The degree to which the wings radially extend from the shaft toward the outer tube also affects the degree to which axial liquid flow is disrupted. In the disclosed embodiment, the wings that protrude radially outwardly from the shaft a distance of about ⅓ the inner diameter of the tube. The distance can be between about ⅕ or xc2xc to about xe2x85x9c or {fraction (5/11)}, and to some extent depends upon the diameter of the shaft from which the member extends.
The volume of the interior of the cylinder (the total interior volume, i.e., the volume without taking into account displacement of free volume by the shaft, cleaning member, etc.) is typically between about 25 and 200 cubic inches, or between about 30 and 180 cubic inches, or between about 40 and 160 cubic inches, or between about 50 and 140 cubic inches, or between about 60 and 120 cubic inches, or between about 60 and 100 cubic inches, or between about 60 and 80 cubic inches, or between about 60 and 70 cubic inches. In the disclosed embodiment, the volume of the cylinder is about (xcfx80xc3x97(1.6/2 in)2xc3x9724 in=) 48 cubic inches (about 786.5 cubic centimetres; or about 0.205 U.S. gallons).
As described in greater detail below, the apparatus of the disclosed embodiment operates satisfactorily at a throughput rate of about 10 gallons per minute.
The inner diameter of the cylinder is preferably between about 1 and 3 inches, or between about 1 and 2.5 inches, or between about 1 and 2 inches, or about 1.5 inches.
The preferred length of the cylinder is between about 6 inches and about 3 feet, or between about 1 foot and 2.5 feet, or between 1.5 feet and 2.5 feet, or about 2 feet.
The cleaning member is of a flexible material. This is because it is in frictional engagement with the inner surface of the window so as to keep the window clean, i.e., transparent to UV light, by removal of any particles or matter that come to settle on or adhere to the inner surface. The material should thus be sufficiently rigid to remove such materials and flexible or pliable so as not to damage the surface. A material that retains these desirable characteristics over time, so as to minimize the need for maintenance or replacement is thus optimal. A material that retains well its original shape over time is said to have good xe2x80x9cmemoryxe2x80x9d. Preferably, the material is a thermoplastic material and, conveniently, the material is a planar sheet. A preferred material is a tetrafluoroethylene fluorocarbon polymer, most preferably the material is Teflon(trademark).
The cleaning member is typically in the shape of a blade, the blade having an edge which extends in substantially continuous contact with the interior surface of the cylinder between first and second longitudinal ends of the tube. The blade is dimensioned such that the edge, when the blade is in relaxed condition, extends radially beyond the inner surface of the cylinder so as force the edge into flexed abutment with the curved interior surface of the tube. The blade is preferably a planar sheet of a tetrafluoroethylene fluorocarbon polymer having a thickness of between about 0.02 and about 0.05 inches, or between a about 0.025 and 0.045 inches. The blade of the preferred embodiment is Teflon(trademark). The preferred blade is about 0.03 inches in thickness and is of constant rectangular cross section, when in relaxed condition.
Preferably, an apparatus of the present invention includes a sensor system that provides an indication of proper and/or improper functioning of the apparatus. There is a first UV radiation sensor trained to receive UV radiation from the UV light source which has not been transmitted through the treatment chamber. There is a second UV radiation sensor trained toward the chamber to receive UV radiation emitted from within the chamber. Means for determining the intensities of UV light received by the first and second sensors so as to determine the effectiveness of treatment of liquid within the chamber are also provided.
In the disclosed embodiment, the first sensor is arranged to receive UV light exclusively from the bulb onto which it is trained and the second sensor is arranged to receive UV light from the chamber without receiving any light emitted directly from a bulb.
Preferably, means is also provided to preclude flow of liquid through the apparatus if it is determined that the liquid flowing through the apparatus might not be subject of satisfactory treatment. If the intensity of the UV signal reaching the sensor trained on the bulb is too low, an unsatisfactory condition is indicated. If the intensity of the UV light detected by the sensor trained on the treatment chamber is too low relative to the UV light detected by the sensor trained on the bulb is too low, an unsatisfactory condition is indicated.
It may be found for certain applications, that an indication of an unsatisfactory condition is suitable while in other applications, an automatic cutoff of the water flow is preferred. An indication of an unsatisfactory condition could be a light (LED) signal, an audio signal, an electrical or digitized optical signal to a household control panel, etc. A device having a warning system compatible with Bluetooth(trademark) technology might be desirable.
In a particular aspect, an apparatus of the present invention includes:
a first UV radiation sensor trained to receive UV radiation from the UV light source which has not been transmitted through the treatment chamber;
a second UV radiation sensor trained toward the chamber to receive UV radiation emitted from therewithin; and
means for determining the intensities of UV light received by the first and second sensors so as to determine the UV transmittance of water through the treatment chamber.
If the intensity of light received by the second sensor relative to the first sensor is too low, i.e., below a predetermined amount, this means that a relatively large amount of light is being absorbed as the light passes through the treatment chamber. This can indicate that the liquid being treated is too murky for effective treatment to be assured. It might also mean that the cleaner is not operating effectively to clean the window, indicating that maintenance is required.
In another aspect, an apparatus of the invention for treating an aqueous liquid such as water with UV light includes:
a pressurized liquid treatment chamber having an inlet end and an outlet end, the chamber being defined by a window permeable to UV light;
a plurality of UV light sources external of the chamber located to emit light through the window into the chamber to expose liquid within the chamber to the emitted light;
a first sensor located and trained to receive UV light emitted from a first of the UV light sources and which has not emerged from the treatment chamber;
a second sensor located and trained to receive UV light emergent from the liquid chamber; and
means for determining the intensity of UV light received by the first sensor relative to the intensity of UV light received by the second sensor so as to determine the effectiveness of the treatment.
There can be an indicator operably connected to the intensity determination means, to provide an indication of when the intensity of UV light received by the first sensor relative to the intensity of UV light received by the second sensor is above a predetermined level.
There can be an indicator operably connected to the first indicator, to provide an indication of when the intensity of UV light received by the first sensor is below a predetermined level.
If the intensity of UV light reaching the first sensor is too low, i.e., below a predtermined amount, this can indicate that light being emitted by the bulb is insufficient to assure adequate treatment of the liquid in the chamber.
The apparatus can include means for precluding flow of said liquid through the treatment chamber, operably connected to a means for determining the intensity of UV light received by the first sensor relative to the intensity of UV light received by the second sensor. A shut-off valve that automatically halts water flow through the apparatus in the case of a possible malfunction of the treatment system can thus be included. It is likely that the valve would be located in-line in advance of the treatment apparatus. This would reduce pressure within the apparatus, and assist in any maintenance operation that requires opening of the treatment chamber.
An apparatus can include UV light sources that are low-pressure mercury lamps. In the disclosed embodiment, the lamps are electrically connected to each other in series.
The treatment chamber, e.g., a quartz tube or hollow cylinder, of the invention preferably can withstand interior liquid pressure of up to about 150 pounds per square inch. The normal pressure range of operation would be between 50 and 140 pounds per square inch, preferably between 50 and 120, or 60 and 100, or 70 and 90, or about 80 pounds per square inch.
A cleaner blade in a preferred aspect of the invention is secured to its shaft along a line parallel to the central axis of a tube, e.g., quartz tube.
In a particular embodiment, the first sensor is trained to directly receive radiation emitted from the first UV light source, and the second sensor is oriented so as not to receive radiation emitted directly from a said light source.
In a preferred apparatus, the window is a quartz sleeve of circular cross section, and the apparatus includes an interior cleaning member having a surface in abutting engagement with an interior surface of the sleeve and moveable with respect thereto for cleaning thereof.
In another aspect, a cleaning member of the invention is mounted on a central shaft so as to be rotatable about a central axis of the sleeve of the treatment chamber, the surface of the cleaning member is in abutting engagement with the interior surface of the sleeve and extends continuously between first and second axial ends of the sleeve, and the member includes a plurality of protrusions located radially intermediate the shaft and the sleeve to promote turbulence of liquid flowing axially through the sleeve.
In another aspect, the invention is a process for treating an aqueous liquid. The process includes passing pressurized liquid through a treatment chamber, the chamber having a window permeable to UV light, an inlet end, and an outlet end. Liquid is treated within the chamber by exposing the liquid to UV light emitted from a UV source external of the chamber. The process includes cleaning an interior surface of the window by turning a shaft located within the chamber, the shaft having a flexible cleaning member affixed thereto, with respect to the window when the member is in flexible engagement with the surface. The shaft includes at least one member extending therefrom so as to disrupt axial flow of water through the chamber from the inlet end to the outlet end.
In a preferred aspect of the method, the window is a cylindrical quartz tube of circular cross section; the shaft extends axially between first and second ends of the tube, and said extending member extends from the shaft toward to the tube a distance equal to at least one quarter the inner diameter of the tube. In the disclosed embodiment, the extending members are wings that protrude radially outwardly from the shaft a distance of about ⅓ the inner diameter of the tube. The distance can be between about ⅕ or xc2xc to about xe2x85x9c or {fraction (5/11)}, and to some extent depends upon the diameter of the shaft from which the member extends.
The extending member can have a surface facing the inlet end with the cross-sectional area of the surface being equal to at least 5 percent of the cross sectional area of the tube. Preferably, there are at least two such extending members, and the combined cross-sectional areas of the extending members are equal to at least 30 percent of the cross sectional area of the tube. Increasing the total cross-sectional area of the surfaces and the degree to which the members extend toward the radially outer portion of the chamber increases the amount of disruption of axial flow of liquid through the chamber from its inlet to outlet end.
In a preferred aspect, the total volume of the interior of a quartz tube of the invention is up to about xc2xc U.S. gallons, the volume occupied by liquid to be treated, e.g., water is at least 50 percent of the total volume of the tube, and the flow rate of the water through the tube is up to about 20 gallons per minute. Usually, the volume is at least {fraction (1/10)} of a gallon and it could be 1 or more gallons. In various aspects, the total volume is between {fraction (1/10)} and 1 gallons, {fraction (1/10)} and xc2xe gallons, {fraction (1/10)} and xc2xd gallons and {fraction (1/10)} and xc2xc gallons.
In a preferred aspect, the pressure of the water within the chamber during treatment is between about 60 and 100 pounds per square inch. In other aspects, the pressure is between 30 and 200, 40 and 180, 50 and 160, 60 and 160, 60 and 150, 60 and 130, 70 and 130, 70 and 110, 70 and 100, 70 and 90 pounds per square inch. The operating pressure is often about 80 pounds per square inch plus or minus 10 pounds per square inch.
In another aspect, an apparatus of the invention includes an impeller rotatably responsive to liquid passing through the apparatus and the shaft to which the cleaning blade is affixed is connected to the impeller for rotation thereof. In this way, movement of the liquid, e.g., water through the treatment chamber provides motive force for the cleaning mechanism.
The cleaning member, e.g., Teflon(trademark) blade can be connected to a central shaft rotatably driven about a central axis of a quartz tube that defines a UV-transmissive window of the treatment chamber.
Simply stated, a flexible cleaning member can be a blade extending between the first and second ends of the sleeve, e.g., circular quartz cylinder of the treatment chamber.
A sleeve of the treatment chamber can be a hollow tube of substantially circular cross section, and the ratio of the inner diameter of the tube to the average outer diameter of the shaft can be between about 10:1 and about 3:1, or between about 10:1 and 5:1 or between about 9:1 and 7:1 or about 8:1.
The blade can be of substantially planar Teflon(trademark) having a UV-transmissivity of at least about 15% percent.
There can be an electric motor operably connected to an end of the shaft to drive rotation of the shaft within the treatment chamber.
A preferred window is a quartz tube having a relatively constant thickness of between about 0.05 and 0.25 inches, preferably about 0.12 inches thick. The outer diameter of the quartz tube is typically between about 1.25 inches and about 5.0 inches.
The blade can be fastened along a first linear edge thereof to the shaft and a surface of the cleaning member in abutting engagement with the interior surface of the sleeve can include a second linear edge of the blade, parallel to the first edge. The blade can be of flexible material which is dimensioned such that the second edge of the blade, when the material is in relaxed condition, extends radially beyond the internal radius of the tube so as to force said second edge into flexed abutment with the curved interior surface of the tube.
The apparatus can include a reflector oriented to direct UV radiation emitted from the UV source(s) toward the treatment chamber, e.g., quartz sleeve.
The second sensor can be oriented so as not to receive radiation emitted directly from a UV source, e.g., a lamp.
The apparatus can include means for blocking flow of liquid through the apparatus when the intensity of radiation received by the first sensor is below a predetermined amount. Such means can be a shut-off valve, biased in the closed position, positively maintained in the open position when the intensity of radiation received by the first sensor is not below the predetermined amount.
In a particular mode of operation, there can be a shut-off valve for blocking flow of liquid through the apparatus, biased in a closed position, positively maintained in an open position (i) when the intensity of radiation received by the first sensor is above a predetermined amount and (ii) when the intensity of radiation received by the second sensor relative to the intensity of radiation received by the first sensor is above a predetermined value; and means for maintaining the valve in the open position when the cleaning member is in a position which obstructs receipt of radiation from the UV radiation source by the second sensor. There can be a first indicator for indicating a condition in which the intensity of radiation received by the first sensor is below a predetermined amount. There can be a second indicator for indicating a condition in which the intensity of radiation received by the second sensor relative to the intensity of radiation received by the first sensor is below a predetermined value.
A particular process of the invention for treating an aqueous liquid, includes the steps of:
passing the liquid under pressure greater than ambient through a treatment chamber;
exposing the liquid in the treatment chamber to UV light emitted from a UV source through a UV-transmissive wall of the treatment chamber;
determining the intensity of the UV light emitted from the light source;
determining the intensity of UV light received by a UV light sensor trained to receive light emerging from the treatment chamber;
determining whether the treatment has a predetermined effectiveness based on the intensity of the UV light emitted from the light source and the intensity of the UV light received by the sensor.
The treatment chamber can include a tubular quartz housing of circular cross section, and the process further includes the steps of passing water under pressure from one axial end to the other of the housing, and rotating a wiper located within the housing about a central axis of the housing against an interior surface of the housing to clean the surface.
The liquid can be supplied to the apparatus under pressure of a municipal water supply.
An apparatus of the invention can be arranged so as to have a xe2x80x9cpredetermined effectivenessxe2x80x9d in operation. In other words, the number of UV lamps, volume and dimensions of the treatment chamber can be determined such that, so long as the rate of water passing through the apparatus does not exceed a certain amount (i.e., the pressure of the water delivered into the apparatus does not exceed a certain maximum) then the operator can be reasonably assured that water emerging from the apparatus has been suitably treated. The apparatus described in the preferred embodiment, for example, operating with a water flow rate of 40 L/min and a percent transmittance of UV light  greater than 75 percent would be produce a UV dose of approximately 80 mJ/cm2.
It will be kept in mind also, that because the sensor array of the preferred embodiment of the present invention, detailed below, includes monitoring the amount of light emerging from liquid subject to treatment, the deleterious effects of turbid water, etc., can also be taken into account in determining the predetermined xe2x80x9cshut-offxe2x80x9d point of the apparatus.
In the preferred embodiment, the wiper shaft is relatively narrow, i.e., has an effective diameter that is about 23 percent of the inner diameter of the quartz housing of the treatment chamber. It will be appreciated that the narrower the shaft, the greater the amount of light distributed throughout the interior of the treatment chamber. In the preferred embodiment, the ratio of the chamber diameter to the shaft diameter is about 4:1. Increasing this ratio would generally increase the effectiveness of the UV light to which the liquid being treated is exposed. A ratio of 10:1 or greater may be achievable, but a ratio as small as 2:1 may still obtain a result that is satisfactory in a particular context. Of course, there is a maximum to the ratio, as the structural integrity of the shaft must be maintained and there is thus a minimum effective diameter of the shaft that must be maintained.
Members affixed with respect to the shaft of the treatment chamber extend radially outwardly into the chamber and provoke turbulence of the liquid flowing through the treatment chamber. This arrangement, which permits inclusion of a relatively narrow shaft as part of a treatment apparatus, permits the usable volume of the treatment chamber to increased. Preferably, an apparatus of the present invention includes a shaft, wiper blade and turbulence inducing members that together take up no more than about 10 or 11 percent of the total volume of the treatment chamber. This leaves about 89 or 90 percent of the total volume of the chamber free to be occupied by liquid to be treated.
An important feature of the preferred embodiment of the present invention is the sensor arrangement. The arrangement provides two functions. A first of the functions is to indicate failure of the UV source. Thus the sensor that is arranged to detect light that has not been subject to the absorbing effects of the liquid in the treatment chamber can be used to provide an indication of when light being emitted from the UV source is insufficient for assured effectiveness of the apparatus. Generally, this sensor is trained directly on the UV source, although it could receive light indirectly via a reflector of some sort, if this was to be advantageous under particular circumstances. A second of the functions is to determine that the amount of light being received within the treatment chamber is sufficient for assured effectiveness of the apparatus. Generally, this function is achieved by use of second sensor that is trained to receive light that has travelled through the treatment chamber and the intensity of the emergent light is used as an indication of whether the treatment is effective. Generally, if the intensity of emergent light is found to be less than a predetermined amount, an indication is given that an xe2x80x9cunsafexe2x80x9d condition may be present. Of course, the apparatus can be provided with an automatic shutoff that would be activated under such a circumstance. The reason for an insufficiently low level of emergent light to come about could be because of a malfunction of the UV light source, turbidity of the liquid within the chamber, etc.
The particular apparatus disclosed herein is designed to operate with the UV lamps on at all times, regardless of whether water is flowing through the quartz tube. It may be advantageous to provide the apparatus with means for turning the lamps off or lowering the power thereto when there is no liquid flow. Such an arrangement could save on power costs and extend lamp life, but care should be taken to ensure that all liquid flowing through the quartz tube is adequately treated.
An apparatus of the present invention also includes means for driving the wiping mechanism. Such a means may be an impeller, where liquid flow itself propels movement of the wiper, or an electric motor could be used. Any suitable means could be provided by a skilled person.